The Effect of Annealing on the Performances of the White Organic Light Emitting Diode (OLED)

A white organic light emitting diode, OLED is one of the approaches to obtained full colour flat screen display. OLED devices with the structure of ITO/PHF:rubrene/Al have been fabricated where poly(9,9-di-n-hexylfluorenyl- 2,7-dyl), PHF used as blue light emitting host and 5,6,11,12-tetraphenyl-napthacene, rubrene as an orange dye dopant. Indium tin oxide, ITO used as anode and aluminium, Al as cathode. The white OLED obtained by varying the concentration of rubrene. The problem occurred by using a dopant is, the turn-on voltage is increased with the dopant concentration. This paper reports the effect of annealing process to the devices at 50degC to 150degC. It was found that the annealing process has reduced the turn-on voltages and increased the brightness. Meanwhile, the colour of light emission was deviated from white to yellowish white.